1. Field of the Invention
The present invention relates to a full toroidal type continuously variable transmission having a full toroid-like groove formed between an input disk and an output disk, and having a friction roller provided in the full toroid-like groove so that the friction roller is in contact with inner surfaces of the input and output disks tiltably and rotatably.
2. Description of the Related Art
The toroidal type continuously variable transmissions are generally divided into a half toroidal type continuously variable transmission and a full toroidal type continuously variable transmission.
In the half toroidal type continuously variable transmission, since the intersection of two tangents at contact points between the friction roller and the input and output disks is located in the vicinity of a center line of the input and output disks, an advantage is provided in which the spin of the contact surface of the friction roller seldom occurs and the power transmission efficiency is satisfactory. On the other hand, since a reaction force of the output disk acts as thrust on the friction roller resulting in a heavy load, and the friction roller rotates at high speed, a problem of heat generation at a bearing arises. In order to prevent the heat generation, a lubricating system for the bearing is proposed as described in Japanese Utility Model Laid Open Publication No. 63-92859 (hereinafter, referred to as a first prior art example).
In this first prior art example, an oil path for lubrication is formed to introduce a lubricating oil to a position adjacent to a friction roller through the inside of a roller supporting member which supports the friction roller. This oil path includes a hole formed in a piston of a hydraulic cylinder which moves the roller supporting member, a gap formed between an outer periphery of a shaft portion of the roller supporting member and an inner periphery of the piston engaging the shaft portion so that the gap is communicated with the hole, and a hole formed in the inside of the roller supporting member so as to communicate with the gap, and the oil path supplies the lubricating oil to the vicinity of a thrust bearing within the friction roller to thereby lubricate the bearing and the friction roller and also to lubricate a rolling surface of the friction roller by the lubricating oil flowing out of the friction roller.
On the other hand, the full toroidal type continuously variable transmission is disclosed, for example, in Japanese Patent Open Publication Hei No. 4-502954 (hereinafter, referred to as a second prior art example).
In this second prior art example, an input disk and an output disk form a full toroid-like groove, and a friction roller is supported by a roller supporting member within the full toroid-like groove so that the friction roller is tiltable and rotatable on a reference line which passes through an intersection between a center axis of the full toroid-like groove and a center axis of the input and output disks, and the friction roller is tilted by a predetermined caster angle with respect to the center axis of the full toroid-like groove, and the roller supporting member is made movable in the axis direction on the reference line by a hydraulic cylinder. However, there is no mention as to a lubricating method of the friction roller, and it is presumed that a lubricating oil is sprayed externally to the friction roller as is the case in general transmissions.
However, in the full toroidal type continuously variable transmission in the second prior art example, it is difficult to sufficiently lubricate in the lubricating system which is performed from the outside, because the position of a contact surface between the input and output disks and the friction roller is moved due to a change in the gear ratio.
Accordingly, it may be considered to apply the internal lubricating system in which the lubricating oil is fed to the inside of the friction roller as is the case in the first prior art example. However, in the full toroidal type continuously variable transmission, since the tangents at the contact points between the input and output disks and the friction roller do not intersect with each other so that the spin increases, and since the power transmission efficiency at the contact surface is low and at the same time, the heat generation at the contact surface is large as compared with the half toroidal type continuously variable transmission, there is an unsolved problem that the lubrication of the contact points between the input and output disks and the friction roller cannot be performed sufficiently even when the lubricating system similar to the first prior art example is adopted.